English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present radial velocities, Fe, and Al abundances for 180 red giant branch(RGB) stars in the Galactic globular cluster Omega Centauri ($\omega$ Cen). Themajority of our data lie in the range 11.0$<$V$<$13.5, which covers the RGBfrom about 1 mag. above the horizontal branch to the RGB tip. The selectionprocedures are biased towards preferentially observing the more metal--poor andluminous stars of $\omega$ Cen. Abundances were determined using equivalentwidth measurements and spectrum synthesis analyses of moderate resolutionspectra (R$\approx$13,000) obtained with the Blanco 4m telescope and Hydramultifiber spectrograph. Our results are in agreement with previous studies aswe find at least four different metallicity populations with [Fe/H]=--1.75,--1.45, --1.05, and --0.75, with a full range of --2.20$\la$[Fe/H]$\la$--0.70.[Al/Fe] ratios exhibit large star--to--star scatter for all populations, withthe more than 1.0 dex range of [Al/Fe] decreasing for stars more metal--richthan [Fe/H]$\sim$--1.4. The minimum [Al/Fe] abundance observed for allmetallicity populations is [Al/Fe]$\sim$+0.15. The maximum abundance of log$\epsilon$(Al) is reached for stars with [Fe/H]$\sim$--1.4 and does notincrease further with stellar metallicity. We interpret these results asevidence for type II SNe providing the minimum [Al/Fe] ratio and a massspectrum of intermediate mass asymptotic giant branch stars causing themajority of the [Al/Fe] scatter. These results seem to fit in the adoptedscheme that star formation occurred in $\omega$ Cen over $>$1 Gyr.

Fe and Al Abundances for 180 Red Giants in the Globular Cluster Omega Centauri (NGC 5139)